The present invention relates to a plate-making method and a plate-making apparatus, which perform digital plate-making, and also relates to a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which perform the digital plate-making on a press and subsequently perform printing. More specifically, the present invention relates to an ink jet plate-making/printing method and an ink jet plate-making/printing apparatus, where in the manufacture of a printing plate, an image is directly formed by an ink jet method of ejecting an oil ink using the electrostatic field and thereby, good image quality can be attained in the plate-making and in the printing.
In the lithographic printing, the printing is performed by forming a printing ink-receptive region and a printing ink-repulsive region on the surface of a printing plate in correspondence to an image original and adhering a printing ink to the ink-receptive region. Usually, hydrophilic and lipophilic (ink-receptive) regions are imagewise formed on the surface of a printing plate and the hydrophilic region is rendered ink-repulsive using a fountain solution.
In general, the recording of an image on a printing original plate (plate-making) is performed by a method of once outputting an image original on a silver salt photographic film in an analog or digital manner, exposing a diazo resin or photopolymerizable photopolymer light-sensitive material (printing original plate) through the film and then, dissolving and removing the non-image area using an alkaline solution.
In recent years, the lithographic printing process is demanded to meet requirements for more improvement in the digital drawing technique and higher efficiency in the process thereof and in order to satisfy these requirements, a large number of systems for directly drawing digital image information on a printing original plate have been proposed. These techniques are called CTP (computer-to-plate) or DDPP (digital direct printing plate). With respect to the plate-making method, for example, a system of recording an image in the light or heat mode using a laser has been proposed and this system is partially put into practical use.
However, in this plate-making method, irrespective of light mode or heat mode, the plate-making generally involves a treatment with an alkaline developer after the laser recording to dissolve and remove the non-image area and therefore, an alkaline waste solution is discharged. This is not preferred in view of the environmental conservation.
As means for realizing an efficient printing process, a system of performing the image drawing on a press is known. Although the above-described method of using a laser may be used, an expensive and large-scale apparatus is necessary. Therefore, a system applying an ink jet method where an inexpensive and compact recording device is used has been proposed.
JP-A-4-97848 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a method of providing a plate drum having a hydrophilic or lipophilic surface part in place of the conventional plate cylinder, forming thereon a lipophilic or hydrophilic image by an ink jet method, and removing and cleaning the image after the completion of printing. In this method, however, it is difficult to attain removal (namely, easy cleaning) of the printing image and a sufficiently long press life at the same time. In the case of forming a printing image having a sufficiently long press life on a plate cylinder, an ink containing a resin in a relatively high concentration must be used and accompanying the evaporation of solvent at the nozzle part, the resin readily fixes to the ink jet means of forming a printing image, as a result, the ink ejection stability decreases and a good image cannot be obtained.
JP-A-64-27953 discloses a method of drawing an image on a hydrophilic plate material by an ink jet method using a lipophilic wax ink, thereby performing the plate-making. In this method, the image is formed by a wax and therefore, the image area is weak in the mechanical strength and deficient in the adhesive property to the hydrophilic surface of the plate material, which gives rise to poor press life.
In the ink jet method of ejecting an oil ink using electrostatic field, ink stirring means is provided in the ink tank so as to prevent the precipitation and coagulation of the ink. The stirring means used is a circulation pump, a stirring blade, an undulator or the like. In the case of a circulation pump, a pump for exclusive use of stirring is generally provided. Since a liquid feed pump for feeding an ink to the ejection head is provided, at least 2 pumps are provided and this is one obstacle to the simplification, miniaturization and reduction in the cost of the apparatus as a whole.
The present invention has been made by taking account of the above-described problems.
A first object of the present invention is to provide a plate-making method and a plate-making apparatus, which can adopt the digital technique not requiring a development processing.
A second object of the present invention is to provide a plate-making method and a plate-making apparatus, where a lithographic printing plate capable of creating a large number of clear and high-quality printed matters can be manufactured inexpensively by a simple and easy method.
A third object of the present invention is to provide a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which can adopt the digital technique not requiring a development processing.
A fourth object of the present invention is to provide a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which can print a large number of clear and high-quality printed matters using an inexpensive apparatus by a simple and easy method.
The present invention also provides a method capable of feeding an ink to the ejection head and at the same time, preventing the precipitation and coagulation of the ink by a construction simpler than that in conventional techniques.
Other objects and effects of the present invention will become apparent from the following description.
The above-described objects of the present invention have been achieved by providing the followings.
1) An ink jet plate-making method comprising:
forming an image directly on a plate material by an electrostatic ink jet method comprising ejecting an oil ink using electrostatic field based on signals of image data; and
fixing said image to manufacture a printing plate,
wherein said process uses:
an ink tank for storing said oil ink,
an ink circulation line for stirring the oil ink stored in said ink tank, and
an ink feed line for feeding said oil ink to an ink jet ejection head, branched from said ink circulation line, and
wherein the ink is circulated to said ink circulation line and thereby stirring of the ink stored in said ink tank and feeding of the ink to said ink jet ejection head are simultaneously performed.
2) The ink jet plate-making method according to item 1) above, wherein an ink recovery line for recovering said oil ink from said ink jet ejection head is provided to connect with said ink circulation line and the ink is recovered from said ink jet ejection head by circulating the ink to said ink circulation line.
3) The ink jet plate-making method according to item 1) or 2) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
4) An ink jet plate-making apparatus comprising:
an image-forming unit which forms an image directly on a plate material based on signals of image data; and
an image-fixing unit which fixes the image formed by said image-forming unit to obtain a printing plate,
wherein said image-forming unit comprises:
an ink jet drawing device having an ink jet ejecting head from which an oil ink is ejected using electrostatic field,
an ink feed member which feeds said oil ink to said ink jet ejection head,
an ink tank for storing said oil ink, and
an ink circulation member for stirring the oil ink stored in said ink tank, and
wherein said ink feed member is branched from said ink circulation member.
5) The ink jet plate-making apparatus according to item 4) above, further comprising an ink recovery member which recovers said oil ink from said ink jet ejection head, wherein said ink recovery member is connected to said ink circulation member.
6) The ink jet plate-making apparatus according to item 4) or 5) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
7) The ink jet plate-making apparatus according to any one of items 4) to 6) above, wherein said image-forming unit further comprises a fixing device for fixing said ink image.
8) The ink jet plate-making apparatus according to any one of items 4) to 7) above, wherein said image-forming unit further has a dust-removing member which removes dusts present on the surface of said plate material at least one of before and during the drawing on said plate material.
9) The ink jet plate-making apparatus according to any one of items 4) to 8) above, further comprising a drum which is rotatable and capable of mounting said plate material thereon so as to perform main scanning by the rotation of said drum.
10) The ink jet plate-making apparatus according to item 9) above, wherein said image-forming unit has an ejection head comprising a single channel head or a multi-channel head and being movable in a direction parallel to an axis of said drum to perform sub-scanning.
11) The ink jet plate-making apparatus according to item 9) above, wherein said image-forming unit has an ejection head comprising a full line head having almost the same length as the width of said plate cylinder.
12) The ink jet plate-making apparatus according to any one of items 4) to 11) above, further comprising an ink temperature-controlling member which controls the temperature of said oil ink and which is provided in said ink tank.
13) The ink jet plate-making apparatus according to any one of items 4) to 12) above, further comprising an ink concentration-controlling member which controls the concentration of said ink.
14) The ink jet plate-making apparatus according to any one of items 4) to 13) above, wherein said ink jet drawing device has an ejection head-retreating or approximating member which approximates said ejection head to said plate cylinder at the drawing on said plate material and retreats said ejection head from said plate cylinder except for the drawing on said plate material.
15) The ink jet plate-making apparatus according to any one of items 4) to 14) above, wherein said image-forming unit has an ejection head-cleaning member which cleans said ejection head at least after the completion of plate-making.
16) A computer-to-cylinder lithographic printing process comprising:
mounting a plate material to a plate cylinder;
forming an image directly on said plate material by an ink jet method comprising ejecting an oil ink using electrostatic field based on signals of image data to manufacture a printing plate; and
performing lithographic printing using said printing plate,
wherein said process uses:
an ink tank for storing said oil ink,
an ink circulation line for stirring the oil ink stored in said ink tank, and
an ink feed line for feeding said oil ink to an ink jet ejection head, branched from said ink circulation line, and
wherein the ink is circulated to said ink circulation line and thereby, stirring of the ink stored in said ink tank and feeding of the ink to said ink jet ejection head are simultaneously performed.
17) The computer-to-cylinder lithographic printing process according to item 16) above, wherein an ink recovery line for recovering said oil ink from said ink jet ejection head is provided to connect with said ink circulation line and the ink is recovered from said ink jet ejection head by circulating the ink to said ink circulation line.
18) The computer-to-cylinder lithographic printing process according to item 16) or 17) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
19) A computer-to-cylinder lithographic printing apparatus comprising:
a plate cylinder for mounting a plate material thereon;
an image-forming unit which forms an image directly on the plate material mounted on said plate cylinder based on signals of image data to manufacture a printing plate having thereon an image; and
a lithographic printing unit which performs lithographic printing using said printing plate,
wherein said image-forming unit comprises:
an ink jet drawing device having an ink jet ejecting head from which an oil ink is ejected using electrostatic field;
an ink feed member which feeds said oil ink to said ink jet ejection head;
an ink tank for storing said oil ink; and
an ink circulation member for stirring the oil ink stored in said ink tank, and
wherein said ink feed member is branched from said ink circulation member.
20) The computer-to-cylinder lithographic printing apparatus according to item 19) above, further comprising an ink recovery member which recovers said oil ink from said ink jet ejection head and which is connected to said ink circulation member.
21) The computer-to-cylinder lithographic printing apparatus according to item 19) or 20) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
22) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 21) above, wherein said image-forming unit has a fixing device for fixing said ink.
23) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 22) above, wherein said image-forming unit has a plate material surface dust-removing member which removes dusts present on the surface of the plate material at least one of before and during the drawing on said plate material.
24) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 23) above, wherein said plate cylinder is rotatable so as to perform main scanning.
25) The computer-to-cylinder lithographic printing apparatus according to item 24) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction parallel to an axis of said plate cylinder so as to perform sub-scanning.
26) The computer-to-cylinder lithographic printing apparatus according to item 24) above, wherein said ejection head comprises a full line head having almost the same length as the width of the plate cylinder.
27) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 26) above, further comprising an ink temperature-controlling member which controls the temperature of the ink and is provided in said ink tank.
28) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 27) above, further comprising an ink concentration-controlling member which controls the concentration of said ink.
29) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 28) above, wherein said ink jet drawing device has an ejection head-retreating or approximating member which approximates said ejection head to said plate cylinder at the drawing on said plate material and retreats said ejection head from said plate cylinder except for the drawing on said plate material.
30) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 29) above, wherein said image-forming unit has an ejection head-cleaning member which cleans said ejection head at least after the completion of plate-making.
31) The computer-to-cylinder lithographic printing apparatus according to any one of items 19) to 30) above, wherein said lithographic printing unit has a paper dust-removing member which removes paper dusts generated at the lithographic printing.